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"Whine" noise coming from 2002 Forester

About 18 months ago the inside boot on the right front axle of my wife's '02 Forester cracked and started to lose the grease. I tried one of the crappy split boot repair kits (it didn't work) and figured I'd just replace the axle when I got a chance. Roughly 8 or 9 months ago I started to hear a faint whining noise when we were driving the car, it wasn't rpm related but speed related, so I figured the axle was getting dry. 6 months ago my wife had a seizure and was not able to drive for 6 months (Missouri law) so the Forester went to her aunt to be a driver for my wife and kids. Since I never saw the car the noise was all but forgotten.
So we get the car back a few days ago, I get in it and the noise is much louder now. I go buy a new axle from O'Reilly and put it in. After learning the hard way that the hole for the roll pin may look like it is aligned but is actually 180* off I got it put back together and go for a drive. The damn noise is still there! I had already checked all of the fluids and the air pressure in the tires when we got it back but didn't realize until today that the front diff had a dip stick. Upon checking the gear oil level when the car was cold it was on the "L" so back to O'Reilly for some 90weight. When I got back home from the test drive the level was now full but slightly foamy.
So my questions would be:What the hell is the noise? I hate to think the front diff is going to crap, the car only had 80,000 miles on it.
Is the slightly foamy gear lube normal or does this indicate it should be changed? Do I need to go by the cold reading of low and add some oil?

this is an odd problem. Does the sound change during a left sweeping turn vs a right sweeping turn? Wheel bearings will make noises when they are going bad. After driving, see if one hub feels warmer than the other. If you have an infrred thermometer, take some readings of the hub area of the wheels after a drive.

Just to be clear, seems like, from the way you mentioned the front diff, this is an automatic? If so, you should know the diff is the stick on the pass side(US) - and the transmission is on the driver's side - right? (hope this is the same arrangement as my wife's Outback)

Are the tires in good condition?(all the same model and wear conditions) maybe inspect the inner edge of the front tires for exposed steel belt. Even rotate them front to back to see if the sound changes.

Are the brake pads worn? Does the sound change with brake application? maybe the squealer on the pad(s) is dragging.

Tires are new, rotors were turned when I put pads on the front last summer. Clearly a gear whine of some sort, sort of like an M-22 rockcrusher, only not as cool. I really thought it was the axle but that was not the case and the fact that it seems to be getting louder has me troubled. Two years ago I had it at the dealer getting the headgaskets replaced (what a nightmare that was but Subaru finally paid for half of the repair) and I really can't afford to go that route or replace the front diff. Not sure how to even go about pin-pointing the problem. I'm not sure what to think of the fluid level. Should I go by the cold reading or the hot? What about the "foam"? I did add about half a quart but I can't see being half a quart low causing the gears to run dry and start making noise as it did register on the stick.

All I can offer at this point is, after I replaced the lube in our Outbacks diff with synth. the whine got a little quieter. This is refereing to the normal whine I could hear - mostly at highway speeds. NOT some condition that came on later, it was always a little noisy.

It does seem as though you have the condition localized so, I suppose some type of repair may be in order. I do agree with you that, a low fluid condition 'might' not lead to the problem you have - though you haven't mentioned how many miles are on the car - or more importantly, how many miles since the last (if ever) front diff fluid check/change. If it was low from the fcatory and never serviced, and you have 100,000 miles - then yeah, I suppose that could be a problem. the devil is in the details.

There is a magnet on the drain plug - inspecting that and perhaps uploading a pic of what that looks like, might get some useful comments from others here with more experience as to what would be 'normal' vs and obvious overabundance of metal shavings. On my car, there was, perhaps, 1/4 teaspoon of material on the magnet. I doubt much more - maybe less.

All I can offer at this point is, after I replaced the lube in our Outbacks diff with synth. the whine got a little quieter. This is refereing to the normal whine I could hear - mostly at highway speeds. NOT some condition that came on later, it was always a little noisy.

It does seem as though you have the condition localized so, I suppose some type of repair may be in order. I do agree with you that, a low fluid condition 'might' not lead to the problem you have - though you haven't mentioned how many miles are on the car - or more importantly, how many miles since the last (if ever) front diff fluid check/change. If it was low from the fcatory and never serviced, and you have 100,000 miles - then yeah, I suppose that could be a problem. the devil is in the details.

There is a magnet on the drain plug - inspecting that and perhaps uploading a pic of what that looks like, might get some useful comments from others here with more experience as to what would be 'normal' vs and obvious overabundance of metal shavings. On my car, there was, perhaps, 1/4 teaspoon of material on the magnet. I doubt much more - maybe less.

I'll try changing the gear oil. The car has 80,000 miles on it and, hangs head low, I've never serviced the front or rear diff. Not even the transfer case. This thing does have a tranfer case, right? I do change the oil on a regular basis and try to keep her clean and polished, though.

I'll try changing the gear oil. The car has 80,000 miles on it and, hangs head low, I've never serviced the front or rear diff. Not even the transfer case. This thing does have a tranfer case, right? I do change the oil on a regular basis and try to keep her clean and polished, though.

your usage is low like both my cars. That is often considered a 'harsh environment' as moisture may not get driven out from fluids well with short/infrequent trips. You might find DIY instructions here or at scoobymods for the front diff. perhaps even a video at youtube.

It wasn't too difficult but I had to buy a T-70 torx from AutoZone ($5 or so IIRC) a 2002 might have a hex-head, not sure when they switched on which models. I also bought a funnel with a hose attached from amazon. I used Lightweight shcokproof synth. but many folks claim the OEM and most other GL-5 fluids in the range mentioned in the owners manual are just fine.

Automatics have a'wet clutch pack' that lives in the same fluid as the tranny. You should consider doing a 'drain/fill' at least on the transmission. That gets about 1/2 the fluid changed. 3 cycles would be considered close enough to a complete change. There are more extensive approaches to transmission fluid change/flush.

Didn't even think about wheel bearings. How difficult is that? In most situations regarding wheel bearings I've dealt with they seem to make more of a grinding sound, deeper pitched and seemed to change tone when you would swerve from side to side, loading and unloading the bearing. We got snow last night and my wife started work today so it might be tomorrow before I can do the lock to lock test.
Keep the suggestions coming. Any good Subaru techs in the Kansas City area?

Does the whine change pitch at all when you accelerate or decelerate? Generally front differential whine will change slightly.
A wheel bearing is more likely to be a steady sound with no change during accel/ decel.

Does the whine change pitch at all when you accelerate or decelerate? Generally front differential whine will change slightly. A wheel bearing is more likely to be a steady sound with no change during accel/ decel.

It is a high pitched sort of whine that gets louder as the car speed increases. That is what leads me to think expensive, I mean, diff.

High pitch is likely to be a differential.
The only thing you can do to buy some time is change the fluid. Pretty simple drain and refill. The condition of the fluid should tell you which diff (front or rear) is making the noise.

As to your question does your car have a transfer case, yes and no.
In the auto trans, there is a transfer unit in the transmission but it is electronically controlled by a solenoid that varies fluid pressure on a set of clutches.
Manual trans has a set of gears and a fluid filled coupling combined into a center differential which balances power output between front and rear driveshafts.
Both however, share the fluid of the transmissions they are built into.

Does the whine change pitch at all when you accelerate or decelerate? Generally front differential whine will change slightly. A wheel bearing is more likely to be a steady sound with no change during accel/ decel.

This is what you need to try next.

Then try the test with the AWD fuse installed. This will switch to 2WD and usually eliminates most noises associated with the rear wheel drive components.

If you have four good quality axle stands and can SAFELY get all 4 wheels off the ground, have a buddy "drive" the car up on stands and listen with a stick or stethescope to the various drivetrain items.

If I end up having to repair the diff, is it easier to rebuild or replace it and how hard is it to get out? Any ballpark price figures? Looks like the engine needs to come out too!

My buddy at work said it could also be the transmission. He suggested the same as smiffy6four and getting it on jackstands and trying to find the cause. I would rather put it on his lift but it is occupied by a '69 Camaro getting a 550hp LS swap:headbang:

Much easier to just replace. Front diff requires disassembly of a large portion of the transmission in order to set the pinion depth correctly. The labor required for this makes it very impractical to replace just the differential. If the diff goes, the whole transmission goes with it.
Rear diff is easy enough to swap. Unbolt old, bolt new (used) in.

i do alot of front diffs the lower pinion berring gets overhated and alows the pinion to move back and forth takes out the diff and the transfer gears is very noisy and whould be a ton of meatal on front diff drain plug magnet i keep diffs in stock for thiss problem the last one was 800 $ for me to rediff a trans for shop tranny was ok except for transfer gears i like to keep the trans matched to car if at all posible. I whould check for meatal on the drain plugs first in none probly somting else axle nut loose ? or damaged hub ? i put that nut very tight 150 or better